Patent GB-1361232-A (GB)
Title: Control apparatus for a machine tool
IPC: G05B19/18
Filed: 1971-07-05
Abstract: 1361232 Programme control of contouring INDUSTRIELLE ELEKTRONIK AGIE LOSONE BEI LOCARNO A G 5 July 1971 [15 July 1970] 31506/71 Heading G3N [Also in Division B3] In a wire erosion machine, Fig.1, symmetrical patterns, such as gear wheels, are cut by programming only a portion of the profile between given end prints, the complete pattern consisting of the portion repeated after rotation through a given angle, the programme for repeated portions being derived by addition, multiplication, and subtraction circuitry from that for the first portion. One such portion may be a gear tooth, or the portion (341-342) Fig. 7 (not shown). Programme control system, Fig. 2. A magnetic or punched tape, or card reader 100 delivers to buffer store 102 data of the profile portion in the form of X and Y values of its end portions together with the interpolation scheme; linear, circular, elliptical, porabola, epi- or hypocycloid, cycloid to be used in joining them. Data concerning the angle α through which the subsequent portions are to be rotated, and a conicity angle #, allowing the angle between the cutting direction and the major surfaces of the workpiece, e.g. for conical or bevel gears, to be varied, is also transmitted. The data is transmitted via control device 116 and optional code converter 103 to a correcting computing unit 104 which converts the profile data to the axis of the wire, displacing the data by the erosion gap plus half the wire diameter. For cuts of constant conicity angle #, the data passes partly via indexing unit 117 to interpolator 105, with return memory 108, controlling machine tables 15, and 16 to produce equal motions of the latter. While the first portion is cut, indexing unit 117 processes the data with the help of angle data α to produce the control data for the next portion, etc. For variable conicity cuts, data passes via conicity computing unit 118 to interpolator 105 to control table 15 and to interpolator 119, with return memory 122, controlling table 16, the difference in the table motions producing variations in the profile conicity. Data passed via unit 116 controls the voltage and current, and the pulsing thereof, of variable width and frequency, single or double pulses, of the erosion generator 114, as well as the flushing of the gap dielectric. A clock pulse generator 113 supplies the various units, including a monitor unit 110  receiving data 111 concerning gap conditions, stopping the drive should a short circuit develop, and causing the machined profile to be traversed in the reverse direction over more than one portion if needed, data therefore being stored in units 108, 122 until the trouble is eliminated. Wire erosion machine, Fig.1. The wire between pins 37 is responsible for the cutting,  the pins being supported on tables 15, 16 respectively, and able to move in X, Y directions with the help of longitudinal and lateral slides 19, 20; 17, 18. Alternatively, shaped electrodes may be used to cut recesses, e.g. for engravings. Electric motor or manually controlled motions in the Z direction are also possible. Synchronous motion of the tables 15, 16 leads to cuts of constant conicity, distinct motions leading to variable conicity. Rotatory and cross movements for the tables, with data in polar co-ordinate form, may be used. Indexing unit 117, Figs.3-6, (not shown). The unit 117, performing logical functions of addition, subtraction and multiplication provides the rotated data; Fig. 6, (not shown). The data from reader 100 may be presented as the sine and cosine of the angle α and the number of rotations to be made; Fig. 3, (not shown) or a set of sines and cosines of the angles α, 2α ---- etc Fig. 4, (not shown) or as the angle α, and number of rotations required, Fig. 5, (not shown), in which case units 105 or 119 are used to interpolate cosine and sine, when not being used in machining. The basic data concerning one portion may be on an endless tape, read for each succeeding portion. Manual controls Manual control unit 107 allows for manual introduction of wire diameter, or electrode thickness and gap width; unit 109 allows for manual table control; unit 115 allows data concerning tolerable degree of roughness, cutting speed, gap width to be fed to monitor unit 110; unit 112 allows manual control of clock generator 113; unit 121 allows modification or introduction of the profile data.